Remove coherent memory from the BL memory maps

This patch extends the build option `USE_COHERENT_MEMORY` to
conditionally remove coherent memory from the memory maps of
all boot loader stages. The patch also adds necessary
documentation for coherent memory removal in firmware-design,
porting and user guides.

Fixes ARM-Software/tf-issues#106

Change-Id: I260e8768c6a5c2efc402f5804a80657d8ce38773
diff --git a/plat/juno/aarch64/juno_common.c b/plat/juno/aarch64/juno_common.c
index 8129b05..7ad40d0 100644
--- a/plat/juno/aarch64/juno_common.c
+++ b/plat/juno/aarch64/juno_common.c
@@ -140,6 +140,7 @@
  * Macro generating the code for the function setting up the pagetables as per
  * the platform memory map & initialize the mmu, for the given exception level
  ******************************************************************************/
+#if USE_COHERENT_MEM
 #define DEFINE_CONFIGURE_MMU_EL(_el)				\
 	void configure_mmu_el##_el(unsigned long total_base,	\
 				  unsigned long total_size,	\
@@ -162,7 +163,25 @@
 								\
 	       enable_mmu_el##_el(0);				\
 	}
-
+#else
+#define DEFINE_CONFIGURE_MMU_EL(_el)				\
+	void configure_mmu_el##_el(unsigned long total_base,	\
+				  unsigned long total_size,	\
+				  unsigned long ro_start,	\
+				  unsigned long ro_limit)	\
+	{							\
+	       mmap_add_region(total_base, total_base,		\
+			       total_size,			\
+			       MT_MEMORY | MT_RW | MT_SECURE);	\
+	       mmap_add_region(ro_start, ro_start,		\
+			       ro_limit - ro_start,		\
+			       MT_MEMORY | MT_RO | MT_SECURE);	\
+	       mmap_add(juno_mmap);				\
+	       init_xlat_tables();				\
+								\
+	       enable_mmu_el##_el(0);				\
+	}
+#endif
 /* Define EL1 and EL3 variants of the function initialising the MMU */
 DEFINE_CONFIGURE_MMU_EL(1)
 DEFINE_CONFIGURE_MMU_EL(3)